sprite-kit - 速度: Meters per second or pixels per second?

Question

苹果documentation指出物理体的速度以米每秒为单位测量。

这是真的吗？像素和米之间有关系吗？如果有的话是什么？

或者这是文档中的错误，它实际上是每秒像素数？

Answer 1

我编写了一个小程序来尝试解决这个问题，并得到了 135 分的答案。

https://stackoverflow.com/a/37523818/1430420

编辑:这是任何人都可以检查我的数学是否错误的程序

//
//  GameScene.swift
//  gravityTest
//
//  Created by Steve Ives on 30/05/2016.
//  Copyright (c) 2016 Steve Ives. All rights reserved.
//

import SpriteKit

class GameScene: SKScene {

//    var elapsedTime: CFTimeInterval = 0.0
    var timeOfLastUpdate: CFTimeInterval = 0.0
    var updateCount = 0
    let sprite = SKSpriteNode(imageNamed:"Spaceship")

    override func didMove(to view: SKView) {
        /* Setup your scene here */

//        physicsWorld.gravity = CGVectorMake(-9.8, 0)

        let location = CGPoint(x: (scene?.frame.midX)!, y: (scene?.frame.midY)!)

        sprite.xScale = 0.5
        sprite.yScale = 0.5

        sprite.physicsBody = SKPhysicsBody(rectangleOf: sprite.size)
        sprite.physicsBody?.isDynamic = true
        sprite.position = location

        self.addChild(sprite)
    }

    override func update(_ currentTime: CFTimeInterval) {
        /* Called before each frame is rendered */
                updateCount += 1
        if (currentTime - timeOfLastUpdate) < 1 {return}

//        if (timeOfLastUpdate - currentTime > 1.0) {
        print("\(updateCount) - Time : \(currentTime) \(currentTime-timeOfLastUpdate) Location is : \(sprite.position) Velocity is : \(sprite.physicsBody!.velocity)")
//        }

        timeOfLastUpdate = currentTime
    }
}